Steel



Patented Feb. 25, 1930 UNITED STATES PATENT OFFICE MARCUS A. GROSSMANN, 0F CANTON, AND DAVID WILLIAMS, OF MASSILLON, OHIO,

ASSIGNORS T0 CENTRAL ALLOY STEEL CORPORATION, OF MASSILLON, OHIO, A COR- PORATION OF NEW YORK STEEL No Drawing.

The present invention has for its object a new and improved steel which shall be less subject to corrosion than steel as now made.

We believe that the corrosion of steel is promoted in part at least'by the presence in it of dissolved nitrogen and iron nitrides as Well as by the presence of dissolved oxygen. This conclusion is based in part on certain work which has recently been done in connection with oxygen determination by the use of the apparatus developed by the Bureau of Standards of the United States. The present invention has to do with the conversion of the dissolved nitrogen and iron nitrides into a crystalline form by which corrosion is not promoted. The element zirconium has the peculiar quality of uniting with dissolved nitrogen and iron nitrides to form zirconium nitride crystals and when this occurs in molten steel the zirconium nitride crystals .are largely carried to the top of the ingot and form a slag or to some extent remain included in the steel, but when so included being inert do not appear to promote corrosion atany rate in an active manner. Accordingly our present invention consists in its broadest aspect in the use of zirconium to convert the dissolved nitrogen and iron nitrides in molten steel, more particularly efiervescing steel, into zirconium nitride crystals. We find in practice however that the ordinary commercial forms of zirconium contain elements which interfere with the effectiveness of the zirconium or produces other detrimental results on the product so that the mere application of ferrozirconium to molten efl'ervescing steel does not appear-to be practical. Ferro-zirconium as ordinarily produced contains silicon, the effect of which on the steel is to cause the elfervescing steel to rise in the. mold so that the ingot is porous and less dense.

, \Ve have found however that the application of ferro-zirconium in the presence of a fluorine compound such as fluorspar (calcium fluoride) or in fact any of the fluorine com pounds except aluminum fluoride tend to cause the eflervescing steel to fall in the mold and thus to counteract the ill eifects of the 1927. Serial No. 209,169.

silicon in the ferro-zirconium. In fact if proper proportions of the fluorine compound are employed an eflervescing steel of exceptional density can be produced. The fluorine compound does not interfere with the action of the zirconium on the dissolved nitrogen and iron nitrides and the result is that We are able to obtain a steel (particularly an efiervescing steel) in which dissolved nitrogen and iron nitrides have been converted into inert zirconium nitride crystals which are either carried off in the slag or remain to a small extent in the metal and that the ingot so produced is exceptionally free from porosity and has a high density.

While we have not yet determined the limits within which the amount of zirconium and fluorine may be varied and still be effective for the purpose intended, we have found that the following proportions give good results. Molten steel 3000 pounds to which is added 4: ounces of commercial 35% ferro-zirconium and 8 ounces of calcium fluoride or fluorspar which are added in the mold after a small amount of the molten steel has been poured into the mold and before it has been filled. While we prefer to add the zirconium and fluorine compounds in the mold it is obvious that it can be added at other times in process of manufacture, for example, in the ladle.

We also believe and knowof no reason to doubt that our invention is applicable not only to pure steels by which we mean steels containing no alloying metal, but also to some at least of the alloy steels containin alloying metals, particularly copper, moly denum and nickel.

What we claim is 1. The method of improving the quality of an efi'ervescing steel which comprises adding a fluorine compound and ferro-zirconium containing silicon.

2. The method of improving the quality of an eflervescing steel which comprises converting the dissolved nitrogen and iron nitrides by the action of ferro-zirconium containing silicon in the presence of a fluorine compound.

3. The method of improving the quality of 

